MUMBAI, Oct. 21 -- A civic activist has moved the Bombay high court challenging the permission granted to fell 520 trees and relocate 2,693 others for the Thane Integral Ring Metro project, alleging that the Thane Municipal Corporation (TMC) gave the clearances without constituting the Tree Authority required under the law. The PIL, filed by social activist Rohit Joshi, challenges the civic body's June 17, 2026, resolution and the permission granted on August 24, 2026. It also seeks the constitution of a Tree Authority for Thane, arguing that tree-felling decisions cannot be made without the prescribed statutory process. Under the Maharashtra (Urban Areas) Protection and Preservation of Trees Act, 1975, municipal authorities are required to constitute a Tree Authority to oversee such decisions. Joshi alleges that the TMC has failed to set up the body and has been "taking all the decisions to grant permissions sought for ling of trees in Thane". This action, he adds, is illegal, arbitrary, and violative of the Constitution of India. An application filed by Joshi under the RTI Act in September revealed that permissions had been granted for projects affecting more than 4,600 trees across Thane in the absence of a Tree Authority, the petition states. The plea says the Metro project would affect around 4,000 trees, of which 2,693 are proposed to be relocated and 519 cut. Nine of the trees marked for relocation are heritage trees, it adds. The project is designed to connect Thane railway station with the upcoming Metro Lines 4 (Wadala-Kasarvadavali) and 5 (Thane-Bhiwandi-Kalyan), improving transport links for the city's growing population. Its groundbreaking ceremony was held ahead of the 2024 Assembly elections. The petition also raises concerns over the alignment's proximity to ecologically sensitive areas. The project site partly falls within 29,871.87 square metres of mangrove land and 40,926.53 square metres of mangrove buffer zone....